1. Field of the Invention
The present invention relates to a method and apparatus for producing and displaying spectrally-multiplexed images of three-dimensional imagery for use in stereoscopic viewing thereof.
2. Brief Description of the Prior Art
The use of stereoscopic imaging in modern times has gained increasing popularity. The reason for this trend in technological innovation is quite clear. At birth, each human being is endowed with the power of stereoscopic vision, and it is this power alone that enables human beings to view the world and all its inhabitants in three dimensions with full depth perception.
Presently, there exist a number of known techniques for recording and displaying stereoscopic images of three dimensional objects and scenery. In the art of video imaging, in particular, two principally different techniques are presently being used to record and display stereoscopic images. The first technique is commonly referred to as "time-multiplexed" or"field-sequential" stereo video or television, whereas the second technique is commonly referred to as "spatially multiplexed" stereo video or television.
In general, each of these stereo imaging techniques involve image recording (i.e. generation) and image display processes. During the image generation process, left and right perspective images (or sequences of perspective images) of 3-D scenery are produced and subsequently recorded on a suitable recording medium. Notably, the recorded left and right perspective images are produced as if actually viewed with the inter-pupil distance of a human observer. Then, during the image display process, the visible light associated with the left and right perspective images is visually presented to the left and right eyes of viewers, respectively, while minimizing the amount of visible light from the left and right perspective images that impinge upon the right and left eyes of the viewer, respectively. As the left and right perspective images of the 3-D scenery are viewed by the left and right eyes of the viewer, a stereoscopic image of the 3-D scenery is perceived, complete with full spatial and depth information of the actual 3-D scenery.
The differences between the above described techniques reside in the manner in which left and right perspective images are "channeled" to the left and right eyes of the viewer in order to preserve stereoscopy. These techniques will be briefly described below.
In 3-D video display systems based upon time-multiplexing principles the left and right perspective images of the 3-D scenery are displayed to viewers during different display periods (i.e. left and right perspective display periods). To ensure that only left perspective images of the 3-D scenery are presented to the left eyes of viewers, the right eye of each viewer is not allowed to view the left perspective image during the left perspective image display period. Similarly, to ensure that only the right perspective images of the 3-D scenery are presented to the right eyes of viewers, the left eye of each viewer is not allowed to view the right perspective image during the right perspective image display period. In the contemporary period, this perspective image "blocking" or selective viewing process is achieved using a pair of liquid crystal light valves (LCLV) as the lenses in special eye wear (e.g. goggles ) worn by each viewer using a 3-D image viewing system based on such principles. Typically, a controller is required in order to drive the left LCLV lens during each left perspective image display period, and drive the right LCLV lens during each right perspective image display period.
In 3-D video display systems based upon spatial-multiplexing principles, left and right perspective images of 3-D scenery are spatially multiplexed during the image generation process in order to produce a spatially multiplexed composite image. Then during the image display process, the visible light associated with the left and right perspective image components of the composite image are simultaneously displayed, but with spatially different "polarizations" imparted thereto. To ensure that only left perspective images of the 3-D scenery are presented to the left eyes of viewers, the right eye of each viewer must not be allowed to view left perspective images. Similarly, to ensure that only the right perspective images of the 3-D scenery are presented to the right eyes of viewers, the left eye of each viewer must not be allowed to view right perspective images. Typically, this perspective image "blocking" or selective-viewing process is achieved using a pair of spatially different polarizing lenses mounted in eye wear (e.g. spectacles) worn by each viewer using a 3-D video display system based on such principles of operation.
While each of these above-described 3-D image display techniques may be used to display 3-D color or gray-scale images, systems based on such techniques are not without shortcomings and drawbacks.
In particular, 3-D image display systems based upon time-multiplexing principles are notoriously plagued by "image flicker" problems. While 3-D video display systems based upon spatial-multiplexing principles are inherently free from the "image flicker" problem associated with time-multiplexed 3-D display systems, spatial-multiplexed 3-D display systems require the use of micropolarizers mounted onto display surfaces (e.g. CRT displays, flat panel liquid-crystal displays, light valve projectors, etc.) from which the polarized light of spatially-multiplexed images emanates. Consequently, this requirement necessitates specially manufactured display and projection surfaces which, in particular applications, can impose undesirable limitations upon the stereoscopic viewing process.
As an alternative to the above-described 3-D image display systems and methods, U.S. Pat. No. 4,995,718 to Jachimowicz, et al. proposes a 3-D color video projection display system using spectral-multiplexing and light polarization principles. Similar to the above-described 3-D image display systems, the proposed 3-D projection display system in U.S. Pat. No. 4,995,718 supports both image recording (i.e. generation) and display processes. However, unlike 3-D image display systems based upon time-multiplexing and spatial-multiplexing principles described above, the 3-D color projection display system of U.S. Pat. No. 4,995,718 exploits the spectral properties of both left and right perspective color images in order to ensure that only left and right perspective color images of a 3-D scenery are seen by the left and right eyes of viewers , respectively, during the image display process. Specifically, during the image generation process, left and right perspective color video images of 3-D scenery are recorded. Then during a first display period in the image projection process, the red and blue spectral components (i.e. magenta) of the left perspective color image are imparted with a first light polarization state and then projected onto a display screen using a first image projector, while the green spectral components of the right perspective color image are imparted with a second light polarization state and projected onto the display screen using a second image projector. During the image projection process of the first display period, the separately projected left and right perspective images must be spatially superimposed (i.e. aligned) in order that these differently polarized spectral components are recombined or "multiplexed" on the projection display screen, which is adapted to preserve the polarization states of the multiplexed spectral components. To ensure that only the magenta spectral components of the left perspective image are presented to the left eyes of viewers during the first display period, while only the green spectral components of the right perspective image are presented to the right eyes of viewers, the viewers are each required to wear spectacles having a left lens characterized by the first polarization state, and a right lens characterized by the second polarization state.
Then during a second display period in the image projection process, the green spectral components of the left perspective color image are imparted with a first light polarization state and then projected onto the display screen using the first image projector, while the magenta spectral components of the right perspective color image are imparted with a second light polarization state and then projected onto the display screen using the second image projector. During the second display period the separately projected left and right perspective images must be spatially superimposed (i.e. aligned) in order that these differently polarized spectral components are recombined (i.e. multiplexed) on the projection display screen. Also, the polarized spectacles worn by each viewer ensures that only the green spectral components of the left perspective image are visually presented to the left eyes of viewers during the first display period, while only the magenta spectral components of the right perspective image are visually presented to the right eyes of the viewers. As the projected spectrally multiplexed images are viewed by the viewers wearing the polarized spectacles during the first and second display periods, a stereoscopic image of the 3-D scenery is perceived, complete with full spatial and depth information of the actual 3-D scenery.
While the 3-D color projection display system disclosed in U.S. Pat. No. 4,995,718 is capable of displaying 3-D stereoscopic color images of 3-D scenery, objects and the like, this prior art system and stereoscopic display technique suffers from several significant shortcomings and drawbacks.
In particular, this prior art approach requires the use of three image projectors in order to project spectrally-filtered, polarized left and right images onto a display screen, upon which the polarized spectral components must recombine during each display period. Such image projection operations require multiple image projectors, a display screen, a large display viewing area, and complicated optical signal processing equipment detailed in the Specification of U.S. Pat. No. 4,995,718.
The method of recording and processing left and right color images required by this prior art stereoscopic display method is generally incompatible with conventional television transmission and distribution schemes.
Moreover, when using this prior art display technique 3-D stereoscopic images cannot be "directly" viewed from CRT display surfaces, flat panel display surfaces, LCD display surfaces, plasma display panel surfaces, electroluminescent panel display surfaces and the like.
Thus, there is a great need in the art for an improved method and system for generating and displaying gray-scaled or color stereoscopic images of 3-D objects, while avoiding the shortcomings and drawbacks of prior art apparatus and methodologies.